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Standard Photometric Systems
Bessell, Michael S.
Standard star photometry dominated the latter half of the twentieth century reaching its zenith in the 1980s. It was introduced to take advantage of the high sensitivity and large dynamic range of photomultiplier tubes compared to photographic plates. As the quantum efficiency of photodetectors improved and the wavelength range extended further to…
My Cruise Through the World of Astronomy
Blaauw, Adriaan
I was born in 1914 in Amsterdam. I grew up there, filling my teenage years with activities as an amateur astronomer. I later studied at Leiden University and volunteered at Leiden Observatory. From 1938 to 1945, I was assistant at the Kapteyn Institute in Groningen, including during the war years 1940 1945, returning to Leiden in October 1945. Aft…
Stellar Structure and Evolution: Deductions from Hipparcos
Lebreton, Yveline
During the last decade, the understanding of fine features of the structure and evolution of stars has become possible as a result of enormous progress made in the acquisition of high-quality observational and experimental data, and of new developments and refinements in the theoretical description of stellar plasmas. The confrontation of high-qua…
The HR Diagram and the Galactic Distance Scale After HIPPARCOS
Reid, I. Neill
The completion and publication of the Hipparcos astrometric catalogue has revitalized studies in many fundamental areas of Galactic structure and stellar evolution. This article reviews the impact of the new parallax results on our understanding of the location of the main-sequence as a function of abundance, of the luminosity calibration of prima…
Reference Frames in Astronomy
Johnston, K. J.; de Vegt, Chr.
Advances in wide-angle astrometric measurements of three to four orders of magnitude in the last thirty years have resulted in a redefinition of the fundamental astronomical reference frame. This new frame, the International Celestial Reference Frame (ICRF), is based on the radio positions of 212 compact extragalactic radio sources. The ICRF defin…
Carbon Stars
Knapp, Gillian R.; Wallerstein, George
Absolute magnitudes are estimated for carbon stars of various subtypes in the Hipparcos catalogue and as found in the Magellanic Clouds. Stellar radii fall within the limits of 2.4-4.7 AU. The chemical composition of carbon stars indicates that the C-N stars show nearly solar C/H, N/H, and ^12C/^13C ratios. This indicates that much of the C and N …
First Results from HIPPARCOS
Kovalevsky, J.
After recalling the principle of the Hipparcos mission and of the data reduction, the main statistical features of the final Hipparcos and Tycho catalogues are presented. The results, characterized by accuracies in annual proper motions and parallaxes of the order of one milliarcsecond have been already widely used for astrophysical investigations…